1. Field of the Invention
The present invention relates to a mounting structure for a semiconductor chip, specifically to a mounting structure wherein a semiconductor chip is mounted directly on an exothermic substrate for a thermal head, a photoreceptor element substrate for an image sensor, or a liquid crystal display substrate in order to provide a semiconductor device in low cost and light weight. The present invention also relates to a mounting method for a semiconductor chip to provide the mounting structure mentioned above.
2. Description of the Prior Art
Conventionally, the driving circuit of a conventional liquid crystal display element and the like is provided with a circuit formed from a copper foil on a glass-epoxy substrate, and is fabricated by soldering to an IC package. Such circuits are attached, one by one, to the electrode on the display substrate by FPC.
In addition, in order to eliminate the glass-epoxy substrate, there is a method known as the TAB method in which the chip is connected to wiring on a flexible substrate using a film of a polyimide type of resin as a base and an electrode terminal provided on the end of the film is connected to an electrode on a display substrate; and also there is a method known as the so-called flip chip method in which a bump of solder is provided on an IC pad and a solder-to-solder connection is performed by providing an opposing electrode with a solder-coated section.
However, because a substrate for a circuit must be provided in addition to a display device, the display product is very difficult to be manufactured in light weight and low cost. In addition, although the TAB method has the objective of providing light weight, there is the problem that the forming of the tape used is too costly.
And in the formation of the solder bump in the flip chip method there is the problem that in order to avoid short circuits between adjacent bumps the degree of integration of the electrode formed on the IC substrate is not increased.
A method has also been proposed in which the substrate and semiconductor chip are electrically connected face down using a photo-cured type resin. However, the thermal expansion of the resin is comparatively large and, when the mounting process is carried out at room temperature(about 25.degree. C.) , poor reliability of the joint section results at high temperatures.
If the electrical wiring is formed by the method of printing a conducting paste directly on a glass substrate or the like, when thermal shock is encountered, broken wires occur because the coefficients of thermal expansion of the substrate and the conducting paste differ by one order of magnitude. In addition, when an organic material on a glass substrate is used as a binder in conductive wiring, migration occurs very easily between the fine wires on the substrate surface, so that long-term reliability is not obtained.